In general, the processing of silver halide photo-graphic light-sensitive materials, for example, the processing of a silver halide color photographic light-sensitive material, comprises fundamental processes of color development, desilvering and image stabilization including water washing. In the color development process, the color developing agent reacts with a silver salt to thereby imagewise produce a dye and developed silver. In the desilvering process, the developed silver produced in the color development process is oxidized (bleached) into a silver salt by a bleaching agent having oxidizing action and removed from the light-sensitive layer by a fixing agent which forms soluble silver together with unused silver halide, or the oxidation into a silver salt and the removal thereof are performed in one stage by a bleach-fixing solution. In the image stabilization process, the atmosphere of the image layer is adjusted to attain the stability of the image formed over a long period of time.
In the black-and-white development, the fundamental process also comprises development, desilvering and water washing.
In respective processing steps, an aqueous solution containing one or more processing chemicals (called a processing solution) is used. Each processing solution is relatively low in the concentration and accordingly, the system where a processing solution usable as it is, is produced by a manufacturer of processing chemicals, transported to a processing laboratory and stored, is generally inadequate in view of profitability, storage space or working.
In order to solve this problem, two methods have been conventionally used. One is a method of preparing a mixture of powder chemicals by mixing processing chemicals constituting the processing solution in a ratio according to the processing solution construction, packaging the mixture to form a so-called solid processing agent, supplying the solid processing agent to a processing laboratory, dissolving it in water at the processing laboratory to have an appropriate concentration, and using the dilution as the processing solution. Another is a method of dissolving the constituent processing chemicals in a high concentration, filling the solution in the liquid and concentrated state into a container to produce a concentrated liquid processing agent, supplying the processing agent to a processing laboratory, diluting it with water to have a predetermined concentration at the laboratory, and using the dilution as a processing solution. The former is specifically described in U.S. Pat. No. 2,843,484. With respect to the latter case, U.S. Pat. No. 3,574,619 describes a concentrated liquid processing agent for color development and U.S. Pat. No. 3,467,521 describes a black-and-white concentrated processing agent.
In recent years, to cope with the requirements for improvement of the productivity in the development processing and for rapid processing, the concentration of the development processing solution rather tends to have a higher concentration. When constituent processing chemicals are contained at a concentration in-excess of the solubility, insoluble components are separated in the solution to present a suspended state. In general, the suspended particle cannot actually have a size of 50 .mu.m or less even if the stirring efficiency is extremely increased. On the contrary, with the passing of time, the particles grow bulky due to the coagulation mechanism or partly the Ostwald ripening mechanism, as a result, they sooner or later become incapable to be floating in the solution and start to precipitate. The precipitate is gradually solidified to lose flowability as the time elapses and turns into a bulky lump or adheres to the wall or bottom of the container, and then the processing solution is no more usable. Accordingly, the liquid and concentrated processing agent must fundamentally be a homogeneous solution having a concentration less than the saturation solubility so that it can be stably stored and used without no problem. Under these circumstances, reduction of volume by concentrating a solution is very hard to attain.
With respect to the liquid concentrated processing agent, pasting of a black-and-white development processing solution has been conventionally known, for example, in U.S. Pat. No. 2,735,774. Further, in the case of a color developer, pasting or concentrating has also been applied for various purposes. U.S. Pat. No. 2,784,086 discloses pasting using an alginic acid derivative as a tackifying agent, namely, a thickener. Japanese Published Unexamined International Application No. 57-500485 discloses a technique of pasting a concentrated liquid processing agent for color development. According to this technique, a processing agent is maintained in the concentrated paste state by adding silicon dioxide, sodium sulfate, lithium sulfate or diatomaceous earth which are photographically inactive. This is, however, accompanied by the increase in the ionic strength and not preferred for the concentrating. The addition of these pasting aids causes useless reduction of the solubility and at the same time, lowers the activity coefficient of the processing solution constituent chemicals.
Furthermore, the pasting is not to elevate the degree of concentration by increasing the solubility of processing chemicals but only delays the separation or if the separation starts, retards the cohesive solidification of insoluble matters to somewhat prolong the use term, and the volume reduction is not substantially solved. On the contrary, since the processing agent is reduced in the flowability, the workability at the processing laboratory is very impaired. In particular, the liquid processing agent loses the advantage such that the dissolving work can be dispensed with.
Accordingly, it was considered that if a processing agent having both the small volume as an advantage of the solid processing agent and the flowability as an advantage of the liquid processing agent is obtained, the above-described problems can be solved and moreover, a liquid development processing agent for silver halide color photographic light-sensitive materials satisfying the requirements in various aspects such as profitability, environmental safety, workability and storage stability can be obtained, which is advantageous in that reduction in the volume of the processing agent, in the weight of the processing agent container, in the space for preservation and storage and in the cost for transportation of the processing agent can be realized, the chemicals can be rapidly and simply dissolved even in chilled water without any splashing or contact on the dissolving working for the preparation of the processing agent, and generation of tar due to air oxidation does not occur during the storage.
The cue for realizing the processing agent having both the small volume as an advantage of the solid processing agent and the flowability as an advantage of the liquid processing agent is a processing agent technique capable of ensuring the aging stability even in the concentrated state and stably performing the production with good reproducibility.
As a result of extensive investigations, the present inventor has found that a concentrated processing agent composition having the advantages both of the liquid processing agent composition and the solid processing composition as described above, namely, capable of maintaining the flowability even in the suspended state, can be realized. However, if the highly concentrated processing agent composition is produced by the usual method where the raw material chemicals are added in sequence to the mixing tank, insoluble suspended particles readily undergo changes by various conditions in the production process, for example, precipitate by coagulation, become bulky or solidify. Therefore, the reproducibility in the production is poor and stable production on a practical level is difficult to attain.